I just started to work for a different Part 135 on demand charter company and apparently they feel that a company other than the charter company can sell tickets and charter the flight with the charter company. I explained that the "other company" had to have the authority to do so such as being a DOT Part 380 operator with economic authority to sell tickets and charter flights from Part 135 companies. I know as a Part 135 on demand we can fly less than 5 round trips scheduled and remain within the realms of our certificate. I need to find something in writing that states that what they are attempting to do is not legal and is libel to get them in trouble. Any help would be greatly appreciated.

Contact an aviation lawyer or search the FAA website for published legal opinions...odds are that this question or similar has come up, and the FAA counsel has rendered an opinion in writing.

Part 135 scheduled operations are just that...scheduled. They operate scheduled operations as part 135. See Surf Air and others or look up part 135 regs

Just because it's 135 does not mean "on demand". Part 135 is quite diverse.

Skyline I understand that. See my post 5 or less scheduled trips are legal, to do more you have to be a 135 commuter or work with a DOT 380 operator which sell the seats then charters your company to do the flight ie. Charter. You can't just have Joe Blow sell your tickets then charter your company to do the flights. Their contention is if Joe Blow sells the tickets and charter us to do the flight we can exceed the 4 round trip restriction. If that were the case why would anybody bother becoming a 135 commuter or applying for a DOT 380. I would like to find something in writing to show them this is not legal.

I join rickair's recommendation to have them consult with an aviation attorney. Whether aviation or any other type of business, especially a regulated business, part of the cost of operations should be a compliance consultation of some sort.

That said, for general information, it sounds like you have a general handle on the potential applicability of Parts 380 and 298. Here's a 2011 Chief Counsel interpretation that while it may or may not be directly applicable to your specific situation, discusses some of the considerations (check the footnotes):

http://www.faa.gov/about/office_org/...rpretation.pdf

There may be an operational control issue there as well. Sounds like they are setting themselves up for something bad.

Okay, I have the answer. A part 135 on demand operator can do less than 5 scheduled flight within a 7 day period selling seats, posting a schedule, departure times, destinations. Our POI would not commit and referred me to Atlanta legal and they directed me to the attorney that handles the South Florida FSDO matters and he said no problem but when I asked for something in writing the answer was no way. The only way to have anything in writing was to have him submit it to Washington and then the ruling would be published on their web site. Seems no one from the FAA will commit to answering any reg questions.